- Joined
- Sep 28, 2002
- Messages
- 39,799
Quote:
You are absolutely right. With a piece of paper over the oil fill hole it flaps in and out.../... Does this mean that since its not just "blowing" that its not really the kind of blow by that you would get from considerably worn rings.
This is almost always the case in a sound engine. If it was a problem, not only would the paper not oscillate, the outflow would be accompanied with oil vapors (or smoke).
Quote:
You did a good job of explaining this concept by the way.
It's a struggle at times. Knowing what you're trying to say ..and saying it in a way that can be understood are challenges for the undisciplined like myself.
To experience true blow by at idle ..as in excessive ..then one MUST SURELY be seeing evidence of it at higher engine speeds and higher cylinder pressures. The engine's ability to cope with blow by is at its maximum at idle. Ample vacuum and minimum cylinder pressure (NO LOAD). The engine is just running out the available air:fuel and expressing it in rpms.
Quote:
Air flow out of oil fill holes when a car is idling varies.
From a slight vacuum, to a wavy neutrality, to a pulsating in/out, to actual blowing out, can all be normal.
Especially with fixed orfice valve or constant flow systems, like old BMWs.
That hole is supposed to be sealed and the engine is running differently than it otherwise would.
Sure. My BMW would not run without the oil cap on ..and would barely run with the dipstick pulled. The crankcase was under full vacuum.
..but under any and all conditions there should never be a net positive pressure out of the crankcase at idle. If it has a metered orifice ..the maximum throughput will be achieved with max vacuum on the manifold side of it ..which is only seen under no load at most sustained engine speeds (until the exhaust backs up) or at idle.
You are absolutely right. With a piece of paper over the oil fill hole it flaps in and out.../... Does this mean that since its not just "blowing" that its not really the kind of blow by that you would get from considerably worn rings.
This is almost always the case in a sound engine. If it was a problem, not only would the paper not oscillate, the outflow would be accompanied with oil vapors (or smoke).
Quote:
You did a good job of explaining this concept by the way.
It's a struggle at times. Knowing what you're trying to say ..and saying it in a way that can be understood are challenges for the undisciplined like myself.
To experience true blow by at idle ..as in excessive ..then one MUST SURELY be seeing evidence of it at higher engine speeds and higher cylinder pressures. The engine's ability to cope with blow by is at its maximum at idle. Ample vacuum and minimum cylinder pressure (NO LOAD). The engine is just running out the available air:fuel and expressing it in rpms.
Quote:
Air flow out of oil fill holes when a car is idling varies.
From a slight vacuum, to a wavy neutrality, to a pulsating in/out, to actual blowing out, can all be normal.
Especially with fixed orfice valve or constant flow systems, like old BMWs.
That hole is supposed to be sealed and the engine is running differently than it otherwise would.
Sure. My BMW would not run without the oil cap on ..and would barely run with the dipstick pulled. The crankcase was under full vacuum.
..but under any and all conditions there should never be a net positive pressure out of the crankcase at idle. If it has a metered orifice ..the maximum throughput will be achieved with max vacuum on the manifold side of it ..which is only seen under no load at most sustained engine speeds (until the exhaust backs up) or at idle.
